This invention relates to internal combustion engines. More particularly although not exclusively it discloses an improved form of free-piston engine.
With known prior art free-piston engines such as those described by M. Goertz and L. Peng in March 2000 SAE Paper 2000-01-0996, entitled FREE-PISTON ENGINE ITS APPLICATION AND OPTIMIZATION, and Galileo Research, Inc. at www.galileoresearch.com, 1999 entitled FREE-PISTON ENGINE-GENERATOR TECHNOLOGY the gas enters the combustion chamber via intake slots through the wall of the cylinder sleeve. This is typical of the method used on most conventional two stroke internal combustion engines. The disadvantage of such intake arrangement is that as the piston rings slide over the intake slots (twice during each stroke) the radial support area is reduced and a slight ring deformation occurs. The deformation results from the elasticity of the unsupported ring material when subjected to radial forces imposed by gas pressure and the pre-tension in the rings. This deformation accelerates the wear rate of the rings and cylinder sleeve and is partly responsible for abandonment of the two stroke engine in modern passenger cars.
It is also known to provide a valve-in-piston arrangement in a reciprocating piston crankcase engine as described in Australian patent application 63021/99 by E. Wechner. Such engines however are are relatively inefficient when used in modern hybrid vehicles as additional mechanical linkage is required to generate the electrical power required for the drive wheels and energy storage cells.
It is therefore an object of this invention to ameliorate the aforementioned disadvantages and accordingly an internal combustion engine is disclosed having at least one pair of longitudinally opposed cylinders with electricity generating stator means fixed relative thereto, respective pistons arranged in said cylinders for cycles of reciprocating compression and power strokes, inlet valve means for introducing air or a fuel mixture into said cylinders prior to said compression strokes, outlet valve means for the expulsion of exhaust gases following said power strokes and said pistons being linked together with a linear actuator for movement therewith whereby during operation of said engine the reciprocating strokes of said pistons and linear actuator with respect to said stator means generates usable electrical energy and said inlet valve means being located in said pistons and comprising a portion of the heads thereof.